[PLAT-6817] Added variable notional builder
[PLAT-6816] Amortising swap example

Also includes [PLAT-6817] Extended variable notional provider
Merge branch 'develop' into topic/PLAT-6816

Conflicts:
	projects/OG-Analytics/src/test/java/com/opengamma/analytics/financial/interestrate/swap/provider/SwapCalculatorE2ETest.java
[PLAT-6816] update expected numbers
Merge pull request #240 from OpenGamma/topic/PLAT-6816

Topic/plat 6816